Control of under-fill using a film during fabrication for a dual-sided ball grid array package

ABSTRACT

Disclosed herein are methods of fabricating a packaged radio-frequency (RF) device. The disclosed methods use a film during fabrication to control the distribution of an under-fill material between one or more components and a packaging substrate. The method includes mounting components to a first side of a packaging substrate and applying a film to a second side of a packaging substrate. The method also includes mounting a lower component to the second side of the packaging substrate and under-filling the lower component mounted on the second side of the packaging substrate with an under-filling agent. The method also includes removing the film on the second side of the packaging substrate and mounting solder balls to the second side of the packaging substrate after removal of the film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/566,844 filed Sep. 10, 2019 and entitled “UNDER-FILL DEFLASH FOR ADUAL-SIDED BALL GRID ARRAY PACKAGE,” which is a continuation of U.S.application Ser. No. 15/885,779 filed Jan. 31, 2018 and entitled“CONTROL OF UNDER-FILL USING UNDER-FILL DEFLASH FOR A DUAL-SIDED BALLGRID ARRAY PACKAGE,” which claims priority to U.S. ProvisionalApplication No. 62/452,450 filed Jan. 31, 2017 and entitled “CONTROL OFUNDER-FILL USING A FILM DURING FABRICATION FOR A DUAL-SIDED BALL GRIDARRAY PACKAGE,” to U.S. Provisional Application No. 62/452,452 filedJan. 31, 2017 and entitled “CONTROL OF UNDER-FILL USING UNDER-FILLDEFLASH FOR A DUAL-SIDED BALL GRID ARRAY PACKAGE,” to U.S. ProvisionalApplication No. 62/452,457 filed Jan. 31, 2017 and entitled “CONTROL OFUNDER-FILL USING A FILM DURING FABRICATION FOR A DUAL-SIDED BALL GRIDARRAY PACKAGE,” to U.S. Provisional Application No. 62/452,458 filedJan. 31, 2017 and entitled “CONTROL OF UNDER-FILL WITH A PACKAGINGSUBSTRATE HAVING AN INTEGRATED TRENCH FOR A DUAL-SIDED BALL GRID ARRAYPACKAGE,” and to U.S. Provisional Application No. 62/452,460 filed Jan.31, 2017 and entitled “CONTROL OF UNDER-FILL USING AN ENCAPSULANT FOR ADUAL-SIDED BALL GRID ARRAY PACKAGE,” each of which is expresslyincorporated by reference herein in its entirety for all purposes.

This application is also related to U.S. Pat. No. 9,381,529 issued Jul.5, 2016 and entitled “SYSTEMS, DEVICES AND METHODS RELATED TO PAINTRECIRCULATION DURING MANUFACTURE OF RADIO-FREQUENCY MODULES,” and toU.S. patent application Ser. No. 15/724,722 filed Oct. 4, 2017 andentitled “DUAL-SIDED RADIO-FREQUENCY PACKAGE WITH OVERMOLD STRUCTURE,”each of which is expressly incorporated by reference herein in itsentirety for all purposes.

BACKGROUND Field

The present disclosure generally relates to fabrication of dual-sidedpackaged electronic modules.

Description of Related Art

The present disclosure relates to fabrication of packaged electronicmodules such as radio-frequency (RF) modules. In radio-frequencyapplications, RF circuits and related devices can be implemented in apackaged module. Such a packaged module can then be mounted on a circuitboard such as a phone board.

SUMMARY

According to a number of implementations, the present disclosure relatesto a method of fabricating a packaged radio-frequency device. The methodincludes mounting components to a first side of a packaging substrate.The method also includes applying a film to a second side of a packagingsubstrate. The method also includes mounting a lower component to thesecond side of the packaging substrate after application of the film.The method also includes under-filling the lower component mounted onthe second side of the packaging substrate with an under-fill agent. Themethod also includes removing the film on the second side of thepackaging substrate. The method also includes mounting solder balls tothe second side of the packaging substrate after removal of the film.

In some embodiments, the film covers contact pads of the solder balls.In some embodiments, applying the film includes laser cutting openingsin a tape adhesive and mounting strips to the film.

The method also includes applying the film includes covering a firstarea of the second side of the packaging substrate while a second areaof the second side of the packaging substrate remains uncovered by thefilm. In further embodiments, the first area includes a plurality ofcontact pads for the solder balls. In further embodiments, the secondarea includes a die area where the lower-component is mounted.

In some embodiments, a size of a keep out zone is reduced by applicationand removal of the film. In some embodiments, the under-fill agent atleast partially covers the film prior to removal of the film. In furtherembodiments, the film prevents the under-fill agent from coating contactpads of the solder balls.

According to a number of implementations, the present disclosure relatesto a method for manufacturing packaged radio-frequency devices. Themethod includes applying a film to an underside of a packagingsubstrate, the packaging substrate having an upper side with one or moreupper components mounted thereto, the underside of the packagingsubstrate having a die area and a contact pad area having a plurality ofcontact pads for through-mold connections, application of the filmincluding covering the contact pad area with the film while leaving thedie area uncovered by the film. The method also includes after applyingthe film, mounting one or more lower components within the die area sothat there is a gap between the one or more lower components and thepackaging substrate. The method also includes after mounting the one ormore lower components, depositing an under-fill material on thepackaging substrate so that the under-fill material penetrates into thegap. The method also includes after depositing the under-fill material,removing the film from the underside of the packaging substrate.

In some embodiments, the method further includes mounting through-moldconnections to the underside of the packaging substrate after removal ofthe film. In further embodiments, the through-mold connections includesolder balls. In yet further embodiments, the method further includessingulating individual units from the packaging substrate to yield aplurality of dual-sided packages.

In some embodiments, the under-fill material includes a sealing resin oran epoxy. In some embodiments, the method further includes curing theunder-fill material. In some embodiments, applying the film includeslaser cutting openings in a tape adhesive and mounting strips to thefilm.

In some embodiments, the film is configured to control distribution ofthe under-fill material during deposition of the under-fill material. Infurther embodiments, the under-fill material contacts the film. Infurther embodiments, removing the film includes removing a portion ofthe under-fill material that covers the film. In further embodiments,removing the film further includes leaving the under-fill materialdeposited in the die area.

According to a number of implementations, the present disclosure relatesto a method of fabricating a packaged radio-frequency (RF) device. Themethod includes mounting components to a first side of a packagingsubstrate. The method also includes mounting a lower component to asecond side of the packaging substrate. The method also includesunder-filling the lower component mounted on the second side of thepackaging substrate with an under-filling agent. The method alsoincludes deflashing a portion of the under-filling agent. The methodalso includes mounting solder balls to the second side of the packagingsubstrate after the portion of the under-filling agent has beendeflashed.

In some embodiments, the portion of the under-filling agent that isdeflashed includes under-filling agent that coats contact pads of thesolder balls. In some embodiments, deflashing includes removing a thinlayer of the under-filling agent. In some embodiments, a size of a keepout zone is reduced by deflashing a portion of the under-filling agentprior to mounting the solder balls.

In some embodiments, the second side of the packaging substrate includesa plurality of contact pads for mounting the solder balls. In furtherembodiments, the under-filling agent coats a portion of at least one ofthe plurality of contact pads. In further embodiments, deflashingincludes removing the portion of the under-filling agent that coats theportion of the at least one of the plurality of contact pads.

According to a number of implementations, the present disclosure relatesto a method for manufacturing packaged radio-frequency devices. Themethod includes mounting one or more lower components on an underside ofa packaging substrate so that there is a gap between the one or morelower components and the packaging substrate, the packaging substratehaving an upper side with one or more upper components mounted thereto,the underside of the packaging substrate having a die area and a contactpad area having a plurality of contact pads for through-moldconnections. The method also includes after mounting the one or morelower components, depositing an under-fill material on the packagingsubstrate so that the under-fill material penetrates into the gap. Themethod also includes after depositing the under-fill material,deflashing a portion of the under-fill material that covers one or moretargeted areas.

In some embodiments, the method further includes mounting through-moldconnections to the underside of the packaging substrate after deflashingthe portion of the under-fill material. In further embodiments, thethrough-mold connections include solder balls. In further embodiments,the methods further includes singulating individual units from thepackaging substrate to yield a plurality of dual-sided packages.

In some embodiments, the under-fill material includes a sealing resin oran epoxy. In some embodiments, the method further includes curing theunder-fill material. In some embodiments, the one or more targeted areasincludes a portion of the contact pad area. In some embodiments,deflashing includes removing a thin layer of the under-fill material. Insome embodiments, a size of a keep out zone is reduced by deflashing aportion of the under-fill material prior to mounting any through-moldconnections to the underside of the packaging substrate.

In some embodiments, the under-fill material coats a portion of thecontact pad area. In further embodiments, deflashing includes removingthe portion of the under-fill material that coats the portion of thecontact pad area.

According to a number of implementations, the present disclosure relatesto a packaging substrate for a packaged radio-frequency (RF) device. Thepackaging substrate includes an insulating material forming a first sideand a second side, the second side forming contact points for a ballgrid array and a lower component, the contact points exposingelectrically conducting material on the second side, the second sidealso forming a dam on the insulating material forming an area to receiveunder-fill agent during an under-fill process, the dam including afeature configured to block the spread of under-fill material during anunder-fill process. The packaging substrate also includes one or moreconducting layers formed within the insulating material. The packagingsubstrate also includes conducting paths electrically coupling contactpads formed on the insulating material to one of the one or moreconducting layers.

In some embodiments, the dam is formed using a solder mask duringfabrication of the packaging substrate. In some embodiments, the dam isphotolithographically defined in the original substrate manufacturingprocess. In some embodiments, the dam includes a plurality ofoutcroppings. In some embodiments, the dam includes continuous elevatedstructures. In some embodiments, the dam includes a plurality ofdisconnected elongated raised features. In some embodiments, the damdefines a keep out region that includes contact points for the lowercomponent and excludes contact points for the ball grid array. In someembodiments, the dam is configured to surround the contact points forthe ball grid array.

According to a number of implementations, the present disclosure relatesto a method of fabricating a packaged radio-frequency (RF) device. Themethod includes mounting components to a first side of a packagingsubstrate. The method also includes mounting a lower component to asecond side of the packaging substrate. The method also includesmounting solder balls to the second side of the packaging substrate. Themethod also includes forming a dam on a second side of the packagingsubstrate after mounting the lower component and after mounting thesolder balls. The method also includes under-filling the lower componentmounted on the second side of the packaging substrate with an under-fillmaterial such that the under-fill material at least partially contactsthe dam formed on the packaging substrate.

In some embodiments, the dam is formed using an application method thatincludes jetting or needle dispensing. In some embodiments, the dam isconfigured to limit the distribution of the under-fill material tomaintain the under-fill material a targeted distance from the solderballs while providing targeted coverage under and around the lowercomponent. In some embodiments, the method further includes singulatingindividual units from the packaging substrate to yield a plurality ofdual-sided packages. In some embodiments, the under-fill materialincludes a sealing resin or an epoxy. In some embodiments, the methodfurther includes curing the under-fill material.

According to a number of implementations, the present disclosure relatesto a method of fabricating a packaged radio-frequency (RF) device. Themethod includes mounting components to a first side of a packagingsubstrate. The method also includes forming a dam on a second side ofthe packaging substrate. The method also includes mounting a lowercomponent to a second side of the packaging substrate after forming thedam. The method also includes mounting solder balls to the second sideof the packaging substrate after forming the dam. The method alsoincludes under-filling the lower component mounted on the second side ofthe packaging substrate with an under-fill material such that theunder-fill material at least partially contacts the dam formed on thepackaging substrate.

In some embodiments, the dam is formed using an application method thatincludes screen printing, jetting, or needle dispensing. In someembodiments, the dam is configured to limit the distribution of theunder-fill material to maintain the under-fill material a targeteddistance from the solder balls while providing targeted coverage underand around the lower component. In some embodiments, the method furtherincludes singulating individual units from the packaging substrate toyield a plurality of dual-sided packages. In some embodiments, theunder-fill material includes a sealing resin or an epoxy. In someembodiments, the method further includes curing the under-fill material.

According to a number of implementations, the present disclosure relatesto a packaging substrate for a packaged radio-frequency (RF) device. Thepackaging substrate includes an insulating material forming a first sideand a second side, the second side forming contact points for a ballgrid array and a lower component, the contact points exposingelectrically conducting material on the second side, the second sidealso forming trenches in the insulating material that include a featureto receive under-fill agent during an under-fill process. The packagingsubstrate also includes one or more conducting layers formed within theinsulating material. The packaging substrate also includes conductingpaths electrically coupling contact pads formed on the insulatingmaterial to one of the one or more conducting layers.

In some embodiments, the trenches are formed using a solder mask duringfabrication of the packaging substrate. In some embodiments, thetrenches do not expose electrically conducting material on the secondside. In some embodiments, the trenches form continuous trenchstructures. In some embodiments, the trenches form a plurality ofdisconnected elongated trenches. In some embodiments, the trenches forma plurality of voids in the substrate. In some embodiments, the trenchesdefine a keep out region that includes contact points for the lowercomponent and excludes contact points for the ball grid array. In someembodiments, the substrate is configured to be singulated to yield aplurality of dual-sided packages.

According to a number of implementations, the present disclosure relatesto a method of fabricating a packaged radio-frequency (RF) device. Themethod includes forming a trench in insulating material of a packagingsubstrate, the trench formed on an underside of the packaging substrate.The method also includes mounting components to an upper side of thepackaging substrate. The method also includes mounting a lower componentto the underside of the packaging substrate. The method also includesmounting solder balls to the underside of the packaging substrate. Themethod also includes under-filling the lower component mounted on thesecond side of the packaging substrate with an under-fill material suchthat the under-fill material at least partially fills the trench formedin the insulating material of the packaging substrate.

In some embodiments, the trench is configured to limit the distributionof the under-fill material to maintain the under-fill material atargeted distance from the solder balls while providing targetedcoverage under and around the lower component. In some embodiments, themethod further includes singulating individual units from the packagingsubstrate to yield a plurality of dual-sided packages. In someembodiments, the under-fill material includes a sealing resin or anepoxy. In some embodiments, the method further includes curing theunder-fill material. In some embodiments, forming the trench includesusing a solder mask process. In some embodiments, the trench includescontinuous trench structures. In some embodiments, the trench includes aplurality of disconnected elongated trenches. In some embodiments, thetrench includes a plurality of voids in the substrate. In someembodiments, forming the trench does not penetrate through theinsulating material to a conductive layer. In some embodiments, thetrench does not include conductive material. In some embodiments, thetrench defines a keep out region that includes contact points for thelower component and excludes contact points for the solder balls.

According to a number of implementations, the present disclosure relatesto a method of fabricating a packaged radio-frequency (RF) device. Themethod includes mounting components to a first side of a packagingsubstrate. The method also includes coating solder balls with a fluxingagent. The method also includes attaching the solder balls to a secondside of the packaging substrate. The method also includes encapsulatingthe solder balls with an encapsulant that forms an obtuse angle with thepackaging substrate. The method also includes attaching a lowercomponent to the second side of the packaging substrate. The method alsoincludes under-filling the lower component mounted on the second side ofthe packaging substrate with an under-filling agent such that theunder-filling agent contacts the encapsulant.

In some embodiments, the encapsulant is a polymer. In some embodiments,the encapsulant is not removed in a cleaning process followingattachment of the solder balls to the packaging substrate. In someembodiments, the encapsulant forms an obtuse angle to the solder balls.In some embodiments, the under-filling agent contacts the encapsulantand not the solder balls. In some embodiments, the method furtherincludes singulating individual units from the packaging substrate toyield a plurality of dual-sided packages.

According to a number of implementations, the present disclosure relatesto a method for manufacturing packaged radio-frequency devices. Themethod includes mounting one or more lower components within a die areaon an underside of a packaging substrate so that there is a gap betweenthe one or more lower components and the packaging substrate, thepackaging substrate having an upper side with one or more uppercomponents mounted thereto, the underside of the packaging substratehaving the die area and a contact pad area having a plurality of contactpads for through-mold connections. The method also includes mounting thesolder balls to the underside of the packaging substrate, the solderballs being coated with a fluxing agent that leaves behind a materialthat encapsulates the base of each solder balls, the material forming anencapsulant. The method also includes after mounting the solder balls,depositing an under-fill material on the packaging substrate so that theunder-fill material penetrates into the gap.

In some embodiments, the encapsulant forms an obtuse angle with asurface of the underside of the packaging substrate and with a surfaceof the solder balls. In further embodiments, the obtuse angle isconfigured to reduce a surface energy driving force for capillary actionof the under-fill material.

In some embodiments, the method further includes singulating individualunits from the packaging substrate to yield a plurality of dual-sidedpackages. In some embodiments, the under-fill material includes asealing resin or an epoxy. In some embodiments, the method furtherincludes curing the under-fill material.

In some embodiments, the encapsulant is configured to controldistribution of the under-fill material during deposition of theunder-fill material. In further embodiments, the under-fill materialcontacts the encapsulant.

In some embodiments, the material is configured so that it is notremoved during a cleaning process that follows solder ball attachreflow. In further embodiments, the material is a polymer. In someembodiments, the encapsulant is configured to reduce capillary actioncausing the under-fill material to wick around the solder balls.

According to a number of implementations, the present disclosure relatesto a packaging substrate for a packaged radio-frequency (RF) device. Thepackaging substrate includes an insulating material forming a first sideand a second side, the second side forming contact points for a ballgrid array and a lower component, the contact points exposingelectrically conducting material on the second side, the second sidealso forming trenches in the insulating material that include a featureto receive under-fill agent during an under-fill process, the secondside also forming a dam on the insulating material forming an area toreceive under-fill agent during an under-fill process, the dam includinga feature configured to block the spread of under-fill material duringan under-fill process. The packaging substrate also includes one or moreconducting layers formed within the insulating material. The packagingsubstrate also includes conducting paths electrically coupling contactpads formed on the insulating material to one of the one or moreconducting layers.

According to a number of implementations, the present disclosure relatesto a method of fabricating a packaged radio-frequency (RF) device. Themethod includes forming a trench in insulating material of a packagingsubstrate, the trench formed on an underside of the packaging substrate.The method also includes forming a dam on the underside of the packagingsubstrate. The method also includes mounting components to an upper sideof a packaging substrate. The method also includes mounting a lowercomponent to the underside of the packaging substrate. The method alsoincludes mounting solder balls to the underside of the packagingsubstrate. The method also includes under-filling the lower componentmounted on the second side of the packaging substrate with an under-fillmaterial such that the under-fill material at least partially flows intothe trench or contacts the dam formed on the packaging substrate.

According to a number of implementations, the present disclosure relatesto a method of fabricating a packaged radio-frequency (RF) device. Themethod includes forming a dam on an underside of the packagingsubstrate. The method also includes mounting components to an upper sideof the packaging substrate. The method also includes mounting a lowercomponent to the underside of the packaging substrate. The method alsoincludes under-filling the lower component mounted on the second side ofthe packaging substrate with an under-fill material such that theunder-fill material at least partially flows into the trench or contactsthe dam formed on the packaging substrate. The method also includesdeflashing a portion of the under-filling agent. The method alsoincludes mounting solder balls to the underside of the packagingsubstrate.

According to a number of implementations, the present disclosure relatesto a method of fabricating a packaged radio-frequency (RF) device. Themethod includes forming a trench in insulating material of a packagingsubstrate, the trench formed on an underside of the packaging substrate.The method also includes mounting components to an upper side of thepackaging substrate. The method also includes mounting a lower componentto the underside of the packaging substrate. The method also includesunder-filling the lower component mounted on the second side of thepackaging substrate with an under-fill material such that the under-fillmaterial at least partially flows into the trench or contacts the damformed on the packaging substrate. The method also includes deflashing aportion of the under-filling agent. The method also includes mountingsolder balls to the underside of the packaging substrate.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features have been described herein. It is to be understoodthat not necessarily all such advantages may be achieved in accordancewith any particular embodiment. Thus, the disclosed embodiments may becarried out in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a dual-sided package having a shielded package and alower component mounted thereto.

FIG. 2 illustrates another example of a dual-sided package having one ormore lower components that can be mounted under a shielded package,generally within a volume defined on an underside of the shieldedpackage.

FIGS. 3A, 3B, 3C, 3D, 3E, 3F, 3G, 3H, and 3I illustrate a typicalprocess flow for fabricating a dual-sided ball grid array package.

FIGS. 4A, 4B, 4C, 4D, 4E, and 4F illustrate a modified fabricationprocess that uses a film to control distribution of an under-fillmaterial.

FIGS. 5A, 5B, 5C, and 5D illustrate a modified fabrication process usingunder-fill deflash to control the distribution of an under-fillmaterial.

FIGS. 6A, 6B, 6C, and 6D illustrate a modified fabrication process thatincludes using a dam to contain an under-fill material.

FIGS. 7A and 7B illustrate a modified fabrication process that uses asubstrate with trenches on the underside of the substrate.

FIGS. 8A and 8B illustrate a modified fabrication process usingencapsulant to control the distribution of an under-fill material.

FIGS. 9A and 9B illustrate a panel with a dam or a series of raisedfeatures in conjunction with a trench or a series of valleys, holes, orthe like in a substrate, wherein the dam and the trench are configuredto control the distribution of an under-fill material.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the claimed invention.

Overview

Described herein are technologies related to fabrication of dual-sidedpackaged electronic modules, such as radio-frequency modules, anddevices, systems, and methods to control the distribution of anunder-fill material between one or more components and a packagingsubstrate. The disclosed technologies include applying a film totargeted areas on the packaging substrate prior to under-filling one ormore components and prior to attaching solder balls. By applying thefilm to the packaging substrate prior to under-filling, the region thatreceives under-fill material can be controlled to a greater degree.After under-filling, the film can be removed to expose clean contactpads for the solder balls. Furthermore, because the solder balls are notpresent during under-fill, there is little capillary action drawingmaterial away from the components being under-filled. This canadvantageously reduce the frequency of voids under the components beingunder-filled. Accordingly, the disclosed systems, devices, and methodscontrol under-fill for dual-sided ball grid array packages using a filmprior to attaching solder balls of the ball grid array.

The disclosed technologies also include under-filling one or morecomponents and deflashing a portion of the under-fill to removeunder-fill material prior to attaching solder balls. By adding thedeflashing step and adding solder balls after deflashing, the regionthat has under-fill material can be controlled to a greater degree. Thedeflashing step removes a thin layer of under-fill material that mayhave coated contact pads for the ball grid array. Furthermore, becausethe solder balls are not present during under-fill, there is littlecapillary action drawing material away from the components beingunder-filled. This can advantageously reduce the frequency of voidsunder the components being under-filled. Accordingly, the disclosedsystems, devices, and methods control under-fill for dual-sided ballgrid array packages using under-fill deflash prior to attaching solderballs of the ball grid array.

The disclosed technologies also include using a dam on a packagingsubstrate. The dam on the packaging substrate is configured to preventor limit the flow of a capillary under-fill material. For example, thedam can form a controlled area so that the capillary under-fill materialfills or flows substantially free within this area but does not flowoutside of the area. This can prevent or limit the capillary under-fillmaterial from flowing onto or contacting other components or elements onthe packaging substrate, such as solder balls of a ball-grid array.Accordingly, the disclosed systems, devices, and methods controlunder-fill for dual-sided ball grid array packages using a dam on apackaging substrate.

The disclosed technologies also include forming a trench in a packagingsubstrate. The trench in the packaging substrate is configured toprevent or limit the flow of a capillary under-fill material. Forexample, the trench can form a controlled area so that the capillaryunder-fill material fills or flows substantially free within this areabut does not flow outside of the area. This can prevent or limit thecapillary under-fill material from flowing onto or contacting othercomponents or elements on the packaging substrate, such as solder ballsof a ball-grid array. Accordingly, the disclosed systems, devices, andmethods control under-fill for dual-sided ball grid array packages usinga trench on a packaging substrate.

The disclosed technologies also include using an encapsulant on solderballs to limit distribution of an under-fill agent. The encapsulant canbe used in the ball attach process. The fluxing agent leaves behind amaterial that encapsulates the base of each solder ball. The encapsulantforms an obtuse angle with the substrate surface and with the ballsurface. This reduces the tendency of the under-fill material to wickaround the solder balls by capillary action. This can prevent or limitthe capillary under-fill material from flowing onto or contacting othercomponents or elements on the packaging substrate, such as solder ballsof a ball-grid array. Accordingly, the disclosed systems, devices, andmethods control under-fill for dual-sided ball grid array packages usingan encapsulant on the solder balls.

In radio-frequency (RF) applications, RF circuits and related devicescan be implemented in a packaged module. Such a packaged module can thenbe mounted on a circuit board such as a phone board. Certain packagedmodules can include dual-sided packages, with components mounted overand under a packaging substrate. Such packaged modules can include anarray of solder balls, or a ball grid array, on an underside of thepackaging substrate, which collectively may be referred to as adual-sided ball grid array (DS-BGA).

FIG. 1 illustrates a dual-sided package 100 having a shielded package102 and a lower component 104 mounted thereto. For the purpose ofdescription, a lower side of the shielded package 102 can include a side103 of a packaging substrate that is to be mounted onto a circuit boardsuch as a phone board. Although not shown separately in FIG. 1, it willbe understood that the shielded package 102 can include such a packagingsubstrate and one or more upper components mounted on its upper side(when oriented as shown in FIG. 1). Accordingly, the dual-sided propertycan include such upper component(s) mounted over the substrate and lowercomponent(s) mounted under the substrate.

The package can be shielded using any suitable shielding method. Forexample, the package 100 can be shielded using a plurality of shieldingwires that are electrically coupled to a ground plane within thepackaging substrate. The package 100 can be shielded using a conformalcoating that is electrically coupled to a ground plane within thepackaging substrate. Any suitable combination of features can be used todefine a shielded volume or region. Such configurations can beimplemented to provide shielding functionality between regions withinand outside of the shielded package 100, and/or between regions that areboth within the shielded package 100.

For the purpose of description, it will be understood that a lowercomponent can include any device that can be mounted on the substrateand/or the circuit board. Such a device can be an active radio-frequency(RF) device or a passive device that facilitates processing of RFsignals. By way of non-limiting examples, such a device can include adie such as a semiconductor die, an integrated passive device (IPD), asurface-mount technology (SMT) device, and the like. In someembodiments, the lower component as described herein can be electricallycoupled to the one or more upper components through, for example, thesubstrate.

FIG. 2 illustrates another example of a dual-sided package 200 havingone or more lower components 204 that can be mounted under a shieldedpackage 202, generally within a volume defined on an underside of theshielded package. In some embodiments, a set of through-mold connections(e.g., one or more through-mold connections) may be implemented, formed,located, and/or positioned on the underside (e.g., side 103 illustratedin FIG. 1) of the shielded package 202. The set of through-moldconnections may define a volume on the underside of the shielded package202. A volume 208 under a shielded package 202 is shown to be defined bythe underside of the shielded package 202 and solder balls 206 of a ballgrid array (BGA). The BGA may be a set of through-mold connections. Forexample, each solder ball 206 of the BGA may be a through-moldconnection in the set of through-mold connections. Other examples ofthrough-mold connections include, but are not limited to solder balls,pillars, columns, posts, pedestals, etc. The through-mold connectionsdescribed herein may also be referred to as contact features. The solderballs 206 allow the dual-sided package 200 to be mounted on a circuitboard 210 such as a phone board. The solder balls 206 can be configuredso that when mounted to the circuit board 210, there is sufficientvertical space between the upper surface of the circuit board 210 andthe lower surface of the shielded package 202 for the lower component204. The volume 208 can be at least partially filled with an over-mold205. The over-mold 205 substantially encapsulates the lower component204. In certain embodiments, at least a portion of the solder balls 206may be exposed through the over-mold 205. Exposing at least a portion ofthe solder balls 206 may provide a connection (e.g., an electricaland/or thermal connection) through the over-mold 205. For example, thesolder balls 206 may provide a connection (e.g., an electricalconnection) to the lower component 204 and/or upper components 224, 226in the shield package 202. In various embodiments, solder (or otherconductive material) may be applied to the exposed portion of the solderballs 206 to form a connection (e.g., electrical connection) with thecircuit board 210. The over-mold 205 may also be referred to as anover-mold structure. In some embodiments, the over-mold 205 and/or thesolder balls 206 (e.g., the exposed portions of the solder balls 206)may form a land grid array (LGA) type/style package.

A close-up view of the solder ball 206 is also illustrated in FIG. 2. Asillustrated in the close-up view of the solder ball 206, the bottom ofthe shielded package includes a pad 215. The pad 215 may be a metallicpad (or some other material) that may provide electrical and/or thermalconductivity between the solder ball 206 and components of the shieldpackage 202 and/or the lower component 204. Solder mask 214 may bedeposited over portions of the pad 215 to define a location where thesolder ball 206 may be formed. The solder ball 206 may be formed (e.g.,implemented, formed, dropped, etc.) on top of the pad 215 and the soldermask 214.

The dual-sided package 200 may be installed on the circuit board 210using the solder ball 206. The solder ball 206 may be attached to thecircuit board 210 (e.g., may be installed, mounted, fixed, etc., to thecircuit board 210) via connection 216. As illustrated in the close-upview of the solder ball 206, the connection 216 may include soldermaterial 221 and pad 219. The solder material 221 may be solder materialfrom the solder ball 206 that is deposited/melted onto the pad 219 whenthe dual-sided package 200 is attached to the circuit board. Forexample, during a reflow process, heat may be applied to melt at least aportion of the solder ball 206 to form the solder material 221. Thesolder material 221 may also include additional material that is formed,implemented, deposited, etc., over the solder ball 206. The pad 219 maybe part of the circuit board 210. The pad 219 may provide electricaland/or thermal conductivity between the dual-sided package 200 and othercomponents/circuits attached to the circuit board 210 (not illustratedin the figures). In some embodiments, the pad 219 may include soldermaterial.

The over-mold 205 has a surface 212 (facing downward toward the circuitboard 210). In some embodiments, the surface 212 may not contact (e.g.,may not physically touch) the surface 213 of the circuit board 210. Forexample, a gap 209 may be present between the surface 212 and thesurface 213. In some implementations, the gap 209 may help protect thelower component 204 from damage when there are linear displacements ofthe dual-sided package 200 due to flexing or dropping. For example, thegap 209 may help protect the lower component 204 from damage as thedual-sided package 200 is installed on the circuit board 200 (e.g., mayprevent the lower component 204 from contacting the surface 213 of thecircuit board 210 during installation/mounting of the dual-sidedpackage). The portion of the over-mold material 205 that covers thelower component 204 may provide additional protection from damage whenthere are linear displacements of the dual-sided package 200 due toflexing or dropping. For example, the over-mold material 205 may alsoprevent the lower component 204 from contacting the surface 213 of thecircuit board 210 during installation/mounting of the dual-sidedpackage. In some embodiments, the gap 209 may also allow the dual-sidedpackage 200 to adapt to process/manufacturing variations when thedual-sided package 200 is installed on the circuit board 210. Forexample, different temperatures may be used to melt the solder ball 206during installation of the dual-sided package. The gap 209 may helpensure that the dual-sided package 200 is properly installed byproviding enough distance between the surface 212 (of over-mold 205) andthe surface 213 (of circuit board 210) while still allowing the soldermaterial of the solder ball 206 to properly bond with the pad 219 of thecircuit board 210. In some embodiments, although the over-mold 205and/or the gap 209 may prevent the component 204 from contacting thesurface 213 (of the circuit board 210), the dual-sided package 200and/or the component 204 may still operate/function properly even if thecomponent 204 does contact the surface 213. For example, the component204 may remain undamaged and/or operable even after contacting thesurface 213 of the circuit board 210.

The dual-sided ball grid array package 200 can include a packagingsubstrate 222 (e.g., a laminate substrate) and a plurality of componentsmounted thereon. For example, a first component 224 can be mounted onthe upper surface of the packaging substrate 222, and electricalconnections between the component 224 and the packaging substrate 222can be facilitated by, for example, wire-bonds 228. In another example,a second component 226 is shown to be mounted on the upper surface ofthe packaging substrate 222 in a die-attach configuration. Electricalconnections between the component 226 and the packaging substrate 222can be facilitated by, for example, die-attach features.

In some embodiments, an under-fill can be provided between the lowercomponent 204 and an underside of the dual-sided package 200. Anunder-fill 230 can be provided between the lower component 204 and theunderside of the package 200 to provide, for example, a more securemounting of the lower component 204.

Examples related to fabrication of dual-sided packages having similarconfigurations are described herein in greater detail. It will beunderstood that although such examples are described in the context ofsolder balls, other types of connection features that provide sufficientvertical space can also be utilized. Although the embodiments, examples,configurations, and/or implementations disclosed herein may refer tosolder balls and/or a BGA, one having ordinary skill in the artunderstands that solder balls and/or a BGA are examples of through-moldconnections. One having ordinary skill in the art understands that othertypes of through-mold connections (e.g., pillars, columns, etc.,) may beused to define a volume on an underside of a shielded package and anover-mold may be implemented in the volume (on the underside of theshielded package). In some embodiments, a through-mold connection (or aset of through-mold connections) may be any structure and/or componentthat may be used to define a volume on the underside of a shieldedpackage and/or may be used to support the shielded package above asurface.

Examples of Fabricating Dual-Sided Ball Grid Array Packages

In a dual-sided ball grid array package structure, a zone is requiredbetween solder ball(s) and integrated circuit chips, dies, or other suchcomponents. This zone (sometimes referred to as a “keep out” zone) is adesign rule that calls out a targeted minimum distance between solderball and component. The keep out zone facilitates meeting manufacturingquality and reliability requirements. Defects such as voids under thecomponent (e.g., an IC chip) where there is no under-fill material, orcontamination of the solder balls with undesired material can occur ifthe keep out zone design rule is violated. It is advantageous to reducethe size of the keep out zone because it can enhance product performanceand/or reduce package size. For example, the overall package size can bereduced and/or the chip size can be increased if the size of the keepout zone can be reduced. Decreasing the package size or increasing chipsize may result in additional or improved functionality per unit area onthe final product motherboard to which the dual-sided ball grid arraypackage is mounted. Accordingly, described herein are systems, devices,and methods that advantageously reduce the keep out zone between solderballs and the IC chip in a dual-sided ball grid array package. Thisresults in greater functionality per unit area when the package ismounted to the final product motherboard.

Typical fabrication techniques attempt to reduce or minimize the ICchip-to-solder ball keep out zone by controlling the capillaryunder-fill dispense process. This may be controlled through the needleselection, the dispense volume, the number of dispense passes, and/orthe dispense temperature. By way of example, the keep out zone on thedispense side of the chip may be about 700 μm, and may be about 200 μmon the other three sides of the chip.

FIGS. 3A-3I illustrate a process flow for fabricating a dual-sided ballgrid array package. FIGS. 3A-3F illustrate a process for completing atop side assembly of a laminate strip (e.g., surface mount, die attach,wire bond, molding, and marking). FIGS. 3G-3I illustrate a process forcompleting a bottom side assembly and forming individual packagesthrough singulation. Optionally, a conformal shield material stack maybe applied to individual packages. As illustrated in FIGS. 4A-4F, thepresent disclosure improves on this fabrication process by applying afilm to the bottom side of the packaging substrate prior tounder-filling to protect the contact pads of the solder balls of theball grid array and to control the distribution of the under-fillingmaterial. In addition, as illustrated in FIGS. 5A-5D, the presentdisclosure improves on this fabrication process by under-filling anddeflashing a portion of the under-fill material prior to adding thesolder balls of the ball grid array. Moreover, as illustrated in FIGS.6A-6D, the present disclosure improves on this fabrication process byforming a dam on the substrate to impede or prevent the capillaryunder-fill material from flowing into the solder balls. Furthermore, asillustrated in FIGS. 7A and 7B, the present disclosure improves on thisfabrication process by forming a trench in the substrate to impede orprevent the capillary under-fill material from flowing into the solderballs. Additionally, as illustrated in FIGS. 8A and 8B, the presentdisclosure improves on this fabrication process by using an encapsulanton the solder balls to impede or prevent the under-fill material fromflowing onto the solder balls.

FIGS. 3A-3I illustrate various stages of a fabrication process in whichdual-sided features can be implemented in a panel format having an arrayof to-be-separated units, and separation of the array into individualunits (also referred to as singulation). Although described in thecontext of BGA-based dual-sided packages, it will be understood that oneor more features of the fabrication technique of FIGS. 3A-3I, 4A-4F,5A-5D, 6A, 6B, 7A, 7B, 8A, and 8B can also be implemented forfabrication of dual-sided packages having other types of mountingfeatures. In some implementations, the disclosed fabrication processescan be utilized for manufacturing dual-sided packages described hereinand in U.S. Pat. No. 9,381,529 and U.S. patent application Ser. No.15/724,722 (each of which has been expressly incorporated by referenceherein).

FIG. 3A illustrates a cross-section view of a panel 300 having aplurality of to-be-singulated units. For example, singulation can occurat boundaries depicted by dashed lines 360 so at to yield singulatedindividual units. The panel 300 includes a substrate 305 on whichcomponents are to be mounted. The substrate 305 can be a laminatesubstrate, a ceramic substrate (e.g., a low-temperature co-fired ceramicsubstrate), or the like. The substrate 305 can include surface features310 that may provide mechanical support. The panel 300 includesconductive material 315 that is configured to provide electricalconnections between conductive layers, surface-mount devices, chips,solder balls, and the like. The conductive material 315 can form contactpads on the upper and lower sides of the substrate 305 to provideelectrical contact points for surface mount devices, chips, solderballs, pillars, any combination of these, or the like. Vias can beformed in the substrate where the conductive material 315 provides anelectrical connection between conductive layers in the panel 300.

FIG. 3B illustrates mounting of surface mount technology (SMT) devices320 such that conductive points on the devices 320 are electricallycoupled to contact pads formed by the conductive material 315 on thepanel 300. By way of example, solder paste can be applied on thesubstrate 305 to allow mounting of one or more SMT devices 320. A reflowoperation can be performed to melt the solder paste to solder the one ormore SMT devices on their respective contact pads. Solder residue fromthe reflow operation can be removed by running the substrates through asolvent or aqueous cleaning step, for example.

FIG. 3C illustrates mounting of a die or chip 325. By way of example,adhesive 326 can be applied on one or more selected areas on thesubstrate 305. The die 325 can be positioned on the selected area withadhesive applied thereon. The adhesive 326 between the die 325 and thedie-mounting area can be cured to secure the die 325.

FIG. 3D illustrates forming electrical connections between the die 325and contact pads using wirebonds 327. The wirebonds 327 can provideelectrical connections for signals and/or power to and from one or morecircuits of the die 325.

FIG. 3E illustrates forming an over-mold 330 over the SMT component(s)320, die(s) 325, and any other upper component on the substrate 305. Byway of example, molding compound can be introduced from one or moresides of a molding volume to form an upper over-molded volume 330. Insome embodiments, the over-mold 330 may completely encapsulate the uppercomponents 320, 325.

FIG. 3F illustrates an optional process of marking the over-mold 330. Byway of example, marking may be accomplished using laser etching orsimilar techniques.

FIG. 3G illustrates attaching a lower component 335 to the underside(which may face upward during fabrication) of the substrate 305. Inaddition, an array of solder balls 340 can be formed on the underside ofthe substrate 305. It will be understood that the lower component 335may be attached for each unit after the array of solder balls 340 isformed, or vice versa. It shall also be understood that the lowercomponent 335 and the array of solder balls 340 may be attached,implemented, and/or formed substantially simultaneously.

FIG. 3H illustrates filling a gap between the lower component 335 andthe substrate 305 with an under-fill agent 345 or an under-fill material(also referred to as under-filling). By way of example, an under-fillmaterial 345, such as a sealing resin or epoxy, can be deposited on thesubstrate 305 and the under-fill material 345 can penetrate into the gapbetween the lower component 335 and the substrate 305 by capillaryforces. The coating shape and amount of under-fill agent 345 varydepending on the package size, pitch, and gap. The under-fill material345 can be cured to provide mechanical support to the lower component335, to provide advantageous thermal properties, to improve solder-ballbonding reliability under external stresses, and the like.

FIG. 3I illustrates singulating individual units to yield a plurality ofdual-sided packages 350 substantially ready to be mounted to circuitboards.

Controlling Under-Fill Using a Film

To better control the size of the keep out area, the fabrication processillustrated in FIGS. 3A-3I can be improved by applying a film to thebottom side of the packaging substrate prior to adding the solder ballsand prior to under-filling the lower component. Upon removal of thefilm, the solder balls can be added. The film protects the contact padsof the solder balls and controls the distribution of the under-fillingagent.

FIGS. 4A-4F illustrate a modified fabrication process, replacing stepsillustrated in FIGS. 3G and 3H. FIG. 4A illustrates a substrate 305 witha die area 337 (e.g., for mounting one or more lower components) and aplurality of solder ball contact pads 342. A film 447 can be added tothe substrate 305 to protect the solder ball contact pads 342 and toexpose the die area 337 for mounting one or more lower components. Theillustration on the left is shown without the film 447 while theillustration on the right is shown with the film 447.

FIG. 4B illustrates the substrate 305 with the film 447 covering thecontact pads 342 prior to addition of the lower component 335 and solderballs 340 and prior to under-filling the lower component 335. The filmcan be used to control the distribution of the under-filling agent,thereby making it possible to reduce the size of the keep out zone.

The process for applying the film 447 to the bottom side of thepackaging substrate 305 can be similar to the process used in shieldingDS-BGA packages. For example, openings can be laser cut in a tapeadhesive. Strips can then be mounted to the film so that the film canprotect the contact pads of the ball grid array from under-fill runout.

FIG. 4C illustrates that, after application of the film 447, the lowercomponent 335 can be added, as described herein with reference to FIG.3G. However, the solder balls of the ball grid array are not mounted tothe substrate 305 as described in FIG. 3G.

FIG. 4D illustrates that, after reflow and cleaning, the under-fillagent 345 can be applied as described herein with reference to FIG. 3H.However, there is a lack of capillary action drawing the under-fillmaterial 345 toward the solder balls because the solder balls are notyet installed. This can reduce the occurrence of under-fill voids underthe lower component 335. In addition, the film 447 prevents theunder-fill material 345 from coating the solder ball contact pads 342.

FIG. 4E illustrates an additional process step of removing the film 447.Removing the film 447 can prevent the under-fill material 345 fromcoating contact pads 342 of the solder balls and/or can remove anyunder-fill material 345 that would have coated those contact pads 342.In this way, the size and extent of the keep out zone can be controlled.

FIG. 4F illustrates that, after removal of the film 447, the solderballs 340 can be added as described in FIG. 3G. The process can thenproceed to reflow again and then to singulate the individual units, asdescribed herein with reference to FIG. 3I.

Controlling Under-Fill Using Deflashing

To better control the size of the keep out area, the fabrication processillustrated in FIGS. 3A-3I can be improved by adding the solder ballsafter under-filling the lower component and deflashing excess under-fillto control the distribution of under-fill agent.

FIGS. 5A-5D illustrate a modified fabrication process, replacing stepsdescribed herein with reference to FIGS. 3G and 3H. In FIG. 5A, a lowercomponent 335 is added as described in FIG. 3G. However, the solderballs of the ball grid array are not mounted to the substrate 305 asdescribed in FIG. 3G. In FIG. 5B, the under-fill material 345 is appliedas described in FIG. 3H. However, there is a lack of capillary actiondrawing the under-fill material 345 toward the solder balls because thesolder balls are not yet installed. This can reduce the occurrence ofunder-fill voids under the lower component 335.

FIG. 5C illustrates an additional process step of deflashing theunder-fill material 345. Deflashing is configured to remove a thin layerof under-fill material from targeted locations 347 on the substrate. Forexample, deflashing can remove under-fill material that may have coatedthe contact pads for the solder balls. In this way, the size and extentof the keep out zone can be controlled. FIG. 5D illustrates that, afterdeflashing, the solder balls 340 can be added as described in FIG. 3G.

Controlling Under-Fill Using a Dam

To better control the size of the keep out area, the fabrication processillustrated in FIGS. 3A-3I can be improved by forming a dam or a seriesof raised features on the substrate 305, wherein the dam or similarfeatures is configured to control the distribution of under-fill agentin the process step illustrated in FIG. 3H.

As illustrated in FIGS. 6A-6C, a panel 600 can be provided wherein thesubstrate 605 includes a dam 607 on the underside of the substrate 605,wherein the dam 607 can be an integral part of the substrate 605 orformed on the substrate 605 at a later time. The dam 607 provides a wayto control the distribution of the under-fill agent during manufacturingof the disclosed double-sided ball grid array packages. The dam 607contains the capillary under-fill material and may prevent it fromcontacting or contaminating the solder balls 340. The dam 607 canprovide a repeatable volume of material to flow under the lowercomponent 335 (e.g., a die), which reduces the frequency of voidingunder the lower component 335. Although the dam 607 is illustrated on asingle side of the solder balls 340, it is to be understood that the dam607 can be configured to surround the solder balls 340. For example, thedam 607 can be configured to have raised features on a plurality ofsides of the solder balls 340. The dam 607 can surround individualsolder balls 340 and/or surround or enclose the area that contains thesolder balls 340.

The substrate 605 can be a laminate substrate, a ceramic substrate(e.g., a low-temperature co-fired ceramic substrate), or the like. Thesubstrate 605 can include surface features 610 that may providemechanical support. The panel 600 includes conductive material 615 thatis configured to provide electrical connections between conductivelayers, surface-mount devices, chips, solder balls, and the like. Theconductive material 615 can form contact pads on the upper and lowersides of the substrate 605 to provide electrical contact points forsurface mount devices, chips, solder balls, pillars, any combination ofthese, or the like. Vias can be formed in the substrate 605 where theconductive material 615 provides an electrical connection betweenconductive layers in the panel 600. The dam 607 can form continuouselevated structures, a plurality of disconnected elongated raisedfeatures, or a plurality of outcroppings in the substrate 605. The dam607 can define one or more keep out areas on the underside of thesubstrate 605.

FIG. 6A illustrates that the dam 607 forms part of the substrate 605. Insome embodiments, the dam 607 can be formed during an additional soldermask process during fabrication of the substrate 605. In someembodiments, the panel 600 includes a substrate 605 having insulatingmaterial forming an upper side and a lower side. The substrate 605 formsvoids in which conducting material electrically couples contact pads toconductive layers or other contact pads. The substrate 605 forms a dam607 (e.g., elevated features, connected raised features, disconnectedraised features, etc.) in the insulating material to form a feature thatcan block the spread of under-fill material during an under-fillprocess. The dam 607 can be photolithographically defined during theoriginal substrate manufacturing process. Then, when assembling thebottom side of the panel 600, the process flow illustrated in FIGS.3A-3I can be used.

FIG. 6B illustrates that the dam 607 can be added to the substrate 605during fabrication after the ball and die attach process steps,illustrated in FIG. 3G. To apply the dam 607, jetting or needledispensing may be used.

FIG. 6C illustrates that the dam 607 can be added to the substrate 605during fabrication before the ball and die attach process steps,illustrated in FIG. 3G. To apply the dam 607, screen printing, jetting,or needle dispensing may be used.

FIG. 6D illustrates the modified process of under-filling in thepresence of the dam 607, compared to the under-filling processillustrated in FIG. 3H. The dam 607 limits the distribution of theunder-fill material 345 to maintain the under-fill material 345 atargeted or desired distance from the solder balls 340 while stillproviding targeted coverage under and around the lower component 335.

Controlling Under-Fill Using a Trench

To better control the size of the keep out area, the fabrication processillustrated in FIGS. 3A-3I can be improved by forming a trench or aseries of valleys, holes, or the like in the substrate 305, whereinthese trenches or similar features are configured to control thedistribution of under-fill agent in the process step illustrated in FIG.3H.

As illustrated in FIG. 7A, a panel 700 can be provided wherein thesubstrate 705 includes trenches 708 on the underside of the substrate705. The trenches provide a way to control the distribution of theunder-fill agent during manufacturing of the disclosed double-sided ballgrid array packages. The substrate 705 can be a laminate substrate, aceramic substrate (e.g., a low-temperature co-fired ceramic substrate),or the like. The substrate 705 can include surface features 710 that mayprovide mechanical support. The panel 700 includes conductive material715 that is configured to provide electrical connections betweenconductive layers, surface-mount devices, chips, solder balls, and thelike. The conductive material 715 can form contact pads on the upper andlower sides of the substrate 705 to provide electrical contact pointsfor surface mount devices, chips, solder balls, pillars, any combinationof these, or the like. Vias can be formed in the substrate 705 where theconductive material 715 provides an electrical connection betweenconductive layers in the panel 700.

To form the trenches 708, vias can be formed in the substrate 705, butinstead of providing conductive paths between conductive layers, thevias for the trenches 708 can provide a void in the substrate structureto receive under-fill agent during the under-fill processing step. Byway of example, the trench 708 can be formed during a solder maskprocess during fabrication of the substrate 705. The trenches 708 canform continuous trench structures, a plurality of disconnected elongatedtrenches, or a plurality of voids or holes in the substrate 705. Thetrenches 708 can define one or more keep out areas on the underside ofthe substrate 705.

In some embodiments, the panel 700 includes a substrate 705 havinginsulating material forming an upper side and a lower side. Thesubstrate 705 forms voids in which conducting material electricallycouples contact pads to conductive layers or other contact pads. Thesubstrate 705 forms trenches 708 (e.g., elongated voids) in theinsulating material to form a feature that can receive under-fillmaterial during an under-fill process. In some embodiments, the trenches708 do not include conductive material or do not penetrate to aconductive layer.

FIG. 7B illustrates the modified process of under-filling in thepresence of trenches 708 in the substrate 705, compared to theunder-filling process illustrated in FIG. 3H. The trenches 708 limit thedistribution of the under-fill material 345 to maintain the under-fillmaterial 345 a targeted or desired distance from the solder balls 340while still providing targeted coverage under and around the lowercomponent 335.

Controlling Under-Fill Using Encapsulant

To better control the size of the keep out area, the fabrication processillustrated in FIGS. 3A-3I can be improved by using a special materialduring the ball attach process illustrated in FIG. 3G. As illustrated inFIG. 8A, a fluxing agent can be used on the solder balls 340 that leavesbehind a material which encapsulates the base of each solder ball 340,forming encapsulant 842. This material may be a polymer. This materialcan be configured so that it is not removed during a cleaning processthat follows solder ball attach reflow. The encapsulant 842 forms anobtuse angle with the surface of the substrate 305 and with the surfaceof the solder balls 340.

When the under-fill material 845 is dispensed in the process stepillustrated in FIG. 8B, it no longer has a tendency to wick around thesolder balls 340 by capillary action. The obtuse angles formed by theencapsulant 842 reduce the surface energy driving force for capillaryaction. This reduces or prevents the under-fill material from flowingaround the solder balls 340. Instead, the under-fill material 345primarily flows under the lower component 335 (e.g., an IC chip).

Controlling Under-Fill Using a Combination of Features

To better control the size of the keep out area, the fabrication processillustrated in FIGS. 3A-3I can be improved by combining features andtechniques described herein with respect to FIGS. 4A-4F, 5A-5D, 6A-6D,7A, 7B, 8A, and 8B. For example, a dam (e.g., as described herein withreference to FIGS. 6A-6D) can be used in combination with a trench(e.g., as described herein with reference to FIGS. 7A and 7B), which isillustrated in FIGS. 9A and 9B. Other combinations can be implemented aswell. For example, the dam can be used in conjunction with a film,deflashing, trench, and/or an encapsulant. As another example, thetrench can be used in conjunction with a film, deflashing, dam, and/oran encapsulant. Similarly, deflashing can be used in conjunction with afilm, dam, trench, and/or an encapsulant. As another example, the filmcan be used in conjunction with deflashing, dam, trench, and/or anencapsulant. Likewise, encapsulant can be used in conjunction with afilm, dam, trench, and/or deflashing.

FIG. 9A illustrates a panel 900 with a dam 907 or a series of raisedfeatures in conjunction with a trench 908 or a series of valleys, holes,or the like in a substrate 905, wherein the dam 907 and the trench 908are configured to control the distribution of under-fill agent 345.

The panel 900 can be provided wherein the substrate 905 includes the dam907 on the underside of the substrate 905, wherein the dam 907 can be anintegral part of the substrate 905 or formed on the substrate 905 at alater time. Similarly, the substrate 905 includes the trench 908 on theunderside of the substrate 905. The dam 907 and the trenches 908 providea way to control the distribution of the under-fill agent 345 duringmanufacturing of the disclosed double-sided ball grid array packages.For example, the combination of the dam 907 and the trenches 908contains the capillary under-fill material 345 and may prevent it fromcontacting or contaminating the solder balls 340. The combination of thedam 907 and the trenches 908 can provide a repeatable volume of materialto flow under the lower component 335 (e.g., a die), which reduces thefrequency of voiding under the lower component 335. Although thecombination of the dam 907 and the trenches 908 is illustrated on asingle side of the solder balls 340, it is to be understood that the dam907 and/or the trenches 908 can be configured to surround the solderballs 340.

The substrate 905 is similar to the substrate 605 and 705 describedherein with reference to FIGS. 6A-6D, 7A, and 7B. For example, thesubstrate 905 can include surface features 910 that may providemechanical support and conductive material 915 to provide electricalconnections between layers and components. The dam 907 can formcontinuous elevated structures, a plurality of disconnected elongatedraised features, or a plurality of outcroppings in the substrate 905. Toform the trenches 908, vias can be formed in the substrate 905, butinstead of providing conductive paths between conductive layers, thevias for the trenches 908 can provide a void in the substrate structureto receive under-fill agent during the under-fill processing step. Thetrenches 708 can form continuous trench structures, a plurality ofdisconnected elongated trenches, or a plurality of voids or holes in thesubstrate 705. The trenches 708 can define one or more keep out areas onthe underside of the substrate 705. The combination of the dam 907 andthe trenches 908 can define one or more keep out areas on the undersideof the substrate 905.

In some embodiments, as described herein with reference to FIG. 6A, thedam 907 can be formed during an additional solder mask process duringfabrication of the substrate 905. In some embodiments, the trench 908can be formed during a solder mask process during fabrication of thesubstrate 905. Then, when assembling the bottom side of the panel 900,the process flow illustrated in FIGS. 3A-3I can be used. In someembodiments, the dam 907 can be added to the substrate 905 duringfabrication after the ball and die attach process steps (e.g., asdescribed herein with reference to FIG. 6B) or the dam 907 can be addedto the substrate 905 during fabrication before the ball and die attachprocess steps (e.g., as described herein with reference to FIG. 6C).

FIG. 9B illustrates the modified process of under-filling in thepresence of the combination of the dam 907 and the trench 908, comparedto the under-filling process illustrated in FIG. 3H. The combination ofthe dam 907 and the trench 908 limits the distribution of the under-fillmaterial 345 to maintain the under-fill material 345 a targeted ordesired distance from the solder balls 340 while still providingtargeted coverage under and around the lower component 335.

Terminology

The present disclosure describes various features, no single one ofwhich is solely responsible for the benefits described herein. It willbe understood that various features described herein may be combined,modified, or omitted, as would be apparent to one of ordinary skill.Other combinations and sub-combinations than those specificallydescribed herein will be apparent to one of ordinary skill, and areintended to form a part of this disclosure. Various methods aredescribed herein in connection with various flowchart steps and/orphases. It will be understood that in many cases, certain steps and/orphases may be combined together such that multiple steps and/or phasesshown in the flowcharts can be performed as a single step and/or phase.Also, certain steps and/or phases can be broken into additionalsub-components to be performed separately. In some instances, the orderof the steps and/or phases can be rearranged and certain steps and/orphases may be omitted entirely. Also, the methods described herein areto be understood to be open-ended, such that additional steps and/orphases to those shown and described herein can also be performed.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Detailed Description using thesingular or plural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list. The word “exemplary” is usedexclusively herein to mean “serving as an example, instance, orillustration.” Any implementation described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otherimplementations.

The disclosure is not intended to be limited to the implementationsshown herein. Various modifications to the implementations described inthis disclosure may be readily apparent to those skilled in the art, andthe generic principles defined herein may be applied to otherimplementations without departing from the spirit or scope of thisdisclosure. The teachings of the invention provided herein can beapplied to other methods and systems, and are not limited to the methodsand systems described above, and elements and acts of the variousembodiments described above can be combined to provide furtherembodiments. Accordingly, the novel methods and systems described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made without departing from the spiritof the disclosure. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fall within thescope and spirit of the disclosure.

What is claimed is:
 1. A method of fabricating a packagedradio-frequency device, the method comprising: mounting components to afirst side of a packaging substrate; applying a film to a second side ofa packaging substrate; mounting a lower component to the second side ofthe packaging substrate after application of the film; under-filling thelower component mounted on the second side of the packaging substratewith an under-fill agent; removing all of the film from the second sideof the packaging substrate; and mounting solder balls to the second sideof the packaging substrate after removal of all of the film.
 2. Themethod of claim 1 wherein the film covers contact pads of the solderballs.
 3. The method of claim 1 wherein applying the film includescovering a first area of the second side of the packaging substratewhile a second area of the second side of the packaging substrateremains uncovered by the film.
 4. The method of claim 3 wherein thefirst area includes a plurality of contact pads for the solder balls. 5.The method of claim 4 wherein the second area includes a die area wherethe lower-component is mounted.
 6. The method of claim 1 wherein a sizeof a keep out zone is reduced by application and removal of the film. 7.The method of claim 1 wherein the under-fill agent at least partiallycovers the film prior to removal of the film.
 8. The method of claim 8wherein the film prevents the under-fill agent from coating contact padsof the solder balls.
 9. A method for manufacturing packagedradio-frequency devices, the method comprising: applying a film to anunderside of a packaging substrate, the packaging substrate having anupper side with one or more upper components mounted thereto, theunderside of the packaging substrate having a die area and a contact padarea having a plurality of contact pads for through-mold connections,application of the film including covering the contact pad area with thefilm while leaving the die area uncovered by the film; after applyingthe film, mounting one or more lower components within the die area sothat there is a gap between the one or more lower components and thepackaging substrate; after mounting the one or more lower components,depositing an under-fill material on the packaging substrate so that theunder-fill material penetrates into the gap; and after depositing theunder-fill material, removing all of the film from the underside of thepackaging substrate.
 10. The method of claim 9 further comprisingmounting through-mold connections to the underside of the packagingsubstrate after removal of the film.
 11. The method of claim 10 whereinthe through-mold connections include solder balls.
 12. The method ofclaim 10 further comprising singulating individual units from thepackaging substrate to yield a plurality of dual-sided packages.
 13. Themethod of claim 9 wherein the under-fill material includes a sealingresin or an epoxy.
 14. The method of claim 9 further comprising curingthe under-fill material.
 15. The method of claim 9 wherein the film isconfigured to control distribution of the under-fill material duringdeposition of the under-fill material.
 16. The method of claim 15wherein the under-fill material contacts the film.
 17. The method ofclaim 16 wherein removing the film includes removing a portion of theunder-fill material that covers the film.
 18. The method of claim 17wherein removing the film further includes leaving the under-fillmaterial deposited in the die area.